Internet Engineering Task Force (IETF) C. Holmberg
Request for Comments: 6228 Ericsson
Category: Standards Track May 2011
ISSN: 2070-1721
Session Initiation Protocol (SIP) Response Code for
Indication of Terminated Dialog
Abstract
This specification defines a new Session Initiation Protocol (SIP)
response code, 199 Early Dialog Terminated, that a SIP forking proxy
and a User Agent Server (UAS) can use to indicate to upstream SIP
entities (including the User Agent Client (UAC)) that an early dialog
has been terminated, before a final response is sent towards the SIP
entities.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6228.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
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Holmberg Standards Track [Page 1]RFC 6228 199 May 2011Table of Contents
1. Introduction ....................................................2
2. Terminology .....................................................4
3. Applicability and Limitation ....................................4
4. User Agent Client Behavior ......................................4
5. User Agent Server Behavior ......................................6
6. Proxy Behavior ..................................................7
7. Backward Compatibility ..........................................9
8. Usage with SDP Offer/Answer .....................................9
9. Message Flow Examples ...........................................9
9.1. Example with a Forking Proxy that Generates 199 ............9
9.2. Example with a Forking Proxy that Receives 200 OK .........10
9.3. Example with Two Forking Proxies, of which One
Generates 199 .............................................11
10. Security Considerations .......................................12
11. IANA Considerations ...........................................13
11.1. IANA Registration of the 199 Response Code ...............13
11.2. IANA Registration of the 199 Option-Tag ..................13
12. Acknowledgements ..............................................13
13. References ....................................................14
13.1. Normative References .....................................14
13.2. Informative References ...................................14
1. Introduction
As defined in RFC 3261 [RFC3261], a Session Initiation Protocol (SIP)
early dialog is created when a non-100 provisional response is sent
to the initial dialog initiation request (e.g., INVITE, outside an
existing dialog). The dialog is considered to be in early state
until a final response is sent.
When a proxy receives an initial dialog initiation request, it can
forward the request towards multiple remote destinations. When the
proxy does that, it performs forking [RFC3261].
When a forking proxy receives a non-100 provisional response, or a
2xx final response, it forwards the response upstream towards the
sender of the associated request. After a forking proxy has
forwarded a 2xx final response, it normally generates and sends
CANCEL requests downstream towards all remote destinations where it
previously forked the request associated with the 2xx final response
and from which it has still not received a final response. The
CANCEL requests are sent in order to terminate any outstanding early
dialogs associated with the request.
Holmberg Standards Track [Page 2]